1. Technical Field
The present invention relates to a test apparatus, an additional circuit, and a test board.
2. Related Art
When testing a device under test such as a semiconductor circuit, a power supply apparatus that supplies current to the device under test sometimes cannot quickly follow fluctuation in the current consumed by the device under test. A known technique for solving this problem, as shown in Patent Document 1, involves providing a bypass capacitor to the power supply line near the device under test.
Patent Document 1: Japanese Patent Application Publication No. 2001-195139
Patent Document 2: U.S. Pat. No. 6,087,843
A bypass capacitor is provided that has a large capacitance, e.g. tens of μF, capable of following a large fluctuation in the power supply current. In order to measure a low current, such as standby current, it is necessary to measure a low output current of the power supply apparatus. In this case, there is a limit on the load capacitance connected to the power supply apparatus, and so a lead relay is provided to disconnect a high-capacitance bypass capacitor from the power supply line.
However, since there are structural limitations near the device under test, a lead relay cannot be provided there. As a result, the high-capacitance bypass capacitor cannot be provided near the device under test, and is instead provided at a distance from the device under test.
Therefore, the power supply line from the bypass capacitor to the device under test is lengthened, which increases the inductance component between the bypass capacitor and the device under test. As a result, it becomes difficult to supply high-frequency current from the bypass capacitor to the device under test.
One test that can be performed for the device under test involves measuring the current consumed when the device under test operates. This test involves measuring the current consumed by the device under test by measuring the current flowing through the power supply line. More specifically, this test involves measuring the current consumed by the device under test by measuring the current flowing through the power supply line on the device under test side of the bypass capacitor.
As described above, however, it is difficult to supply high-frequency current from the high-capacitance bypass capacitor to the device under test. Therefore, even when measuring the current flowing through the power supply line between the high-capacitance bypass capacitor and the device under test, it is difficult to accurately measure the current consumed by the device under test operating at a high frequency.